Extending sticky-Datalog<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" id="d1e182" altimg="si10.svg"><mml:msup><mml:mrow /><mml:mrow><mml:mo>±</mml:mo></mml:mrow></mml:msup></mml:math> via finite-position selection functions: Tractability, algorithms, and optimization

Weakly-Sticky(WS) Datalog+/- is an expressive member of the family program classes that defined on basis conditions stickiness and weak-acyclicity. Conjunctive query answering (QA) over WS programs has been investigated, its tractability in data complexity established. However, design implementation practical QA algorithms their optimizations have open. In order to fill this gap, we first study Sticky from point view behavior chase procedure. We extend property generalized (GSCh) modulo oracle selects (and provides) predicate positions where finitely values appear during chase. Stickiness a selection function S provides only subset those defines sch(S), semantic subclass GSCh. Program with functions include WS, another syntactic class introduce characterize, namely JWS, jointly-weakly-sticky programs, which contains WS. The for these last three are computable, no external, possibly non-computable needed. propose bottom-up algorithm general S. As particular case, obtain polynomial-time JWS weakly-sticky programs. Unlike turns out be closed under magic-sets optimization. consequence, both generic magic-set optimization can particularized applied